Method and means for reducing the response time of magnetic valves

ABSTRACT

A method and apparatus for reducing the response times of electromagnetically controlled valves. The operating coil of the valve has a center tap connected to a D.C. supply voltage, whereas the end terminals of the coil are each connected to the collectors of two power transistors. The base supply voltages for the power transistors are derived from a voltage divider, and a control transistor has its emitter-collector path connected across the base voltage supply of the power transistors. The power transistors are connected to function as an astable multivibrator which is turned on and off by the control transistor. The astable multivibrator provides rectangular-shaped alternating voltage to the operating coil of the valve for demagnetizing the valve before or after operation of actuation of the valve.

United States Patent Melcher et al. 1 May 30, 1972 54] METHOD AND MEANSFOR REDUCING 3,334,316 8/1967 Price ..331/113 x RESP N E ME 0F MAGNET! IE O S TI C FOREIGN PATENTS OR APPLICATIONS 1,318,728 1 1963 F ..251 141[72] Inventors: Kurt Melcher, Markgroeningen; Wilhelm fame Vogel,Stuttgart-Bad Cannstatt, Germany Examiner Amold Rosemhal [73] Assignee:Robert Bosch GmbH, Stuttgart, Germany Alt rney-Michael S. Striker 22Filed: Apr. 14, 1970 [57] ABSTRACT [21] App! 32495 A method andapparatus for reducing the response times of eiectromagneticallycontrolled valves. The operating coil of [30] Foreign ApplicationPriority Data the valve has a center tap connected to a DC. supplyvoltage, whereas the end terminals of the coil are each connected toApr. 18, 1969 Germany ..P 19 19 702.5 the collectors of two powertransistors The base supply ages for the power transistors are derivedfrom a voltage di- [52] U.S.Cl Vidal, and a comm transistor has itsemittepconecmr path 2; 51/129 137/487 connected across the base voltagesupply of the power 1 o 3 17/1 5 l23' 33 1 ll transistors. The powertransistors are connected to function as an astable multivibrator whichis turned on and off by the con- 56 R f Cited trol transistor. Theastable multivibrator provides rectangular- 1 e erences shapedalternating voltage to the operating coil of the valve UNITED STATESPATENTS for de-magnetizing the valve before or after operation ofactuation of the valve. 3,458,769 7/1969 Stampfli ..25l/3O X 3,219,09511/1965 Nilson ..25i/l29 X 3 Claims, 5 Drawing Figures PATENTEDMAY 30 m2SHEET 10F 2 III" INVENTORS Kurt MELCHER Wilhelm VOGEL their ATTORNEYPATEHIEUmso I972 3.666 232 UUUUUUUUHHHHUUU INVENTORS Kurt MELCHE Wilhe mVOC-E.

their ATTORNEY BACKGROUND OF THE INVENTION The present invention relatesto a process for reducing the response time of magnetic valves, and anarrangement for carrying out the process.

It is often required that magnetic valves have an extremely shortresponse time. Magnetic valves with short response times are installedin electronically controlled fuel injection arrangements for internalcombustion engines. This applies particularly to high-speed machines.Means for shortening the response time of magnetic valvesare alreadyknown in the art. Such conventional means consists, for example, ofreducing the masses of the movable parts subjected to the magneticforces, and to increase the surfaces upon which the magnetic forces areapplied. The conventional means, furthermore, involves reduction of theinductance of the operating coils.

It is an object of the present invention, accordingly, to reduce theresponse times of magnetic valves by reducing the complexity of theconventional arrangements. The solution to the problem resides in aprocess through which the operating coil of the magnetic valve hasapplied to it an alternating voltage of predetermined frequency after orbefore each actuation of the valve. This alternating voltage serves tode-magnetize the valve.

An arrangement for carrying out the process, in accordance with thepresent invention, consists of providing an oscillator which isconnected to the operating coil of the magnetic valve and which may beturned on and off, in accordance with the actuation of the valve. Anadvantageous operation of the valve is realized when, in accordance witha further feature of the present invention, the output voltage of theoscillator is substantially of rectangular-shaped form. The powerreceived by the operating coil of the magnetic valve within apredetermined time interval, is as a first approximation, proportionalto the time integral of the applied voltage. The time integral isevidently larger for a rectangular-shaped alternating voltage, withoutgaps, than for a sinusoidal-shaped voltage of equal amplitude andotherwise comparable conditions. An astable multivibrator is used toprovide simple and reliable operation of an oscillator.

SUMMARY OF THE INVENTION A method and arrangement for reducing theresponse time of an electromagnetically operated valve. The valve has acenter-tapped coil, with the center tap connected to a source of D.C.operating voltage. The end terminals of the electromagnetic coil of thevalve are each connected to one collector of two power transistors whichfunction together in the form of an astable multivibrator. The basevoltage supply for the power transistors is derived from a voltagedivider having one common resistor connected to the D.C. voltage source.Two separate resistors are connected to the bases of the powertransistors and to the common resistor. A control transistor isconnected across the base voltage supply for the two power transistors.The astable multivibrator serves to apply a substantiallyrectangular-shaped alternating voltage to the coil for the purpose ofde-magnetizing the ferromagnetic parts of the valve. De-magnetization ofthe valve is applied either before or after actual operation oractuation of the valve in usage.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electrical schematicdiagram for de-magnetization of a magnetic valve through the use of anoscillator, in accordance with the present invention;

FIG. 2 and FIG. 2a illustrate the magnetic characteristics relative tothe operation of the circuit arrangement of FIG. 1;

FIG. 3 is a voltage-time diagram of the control voltage of theoscillator, whereby the oscillator is switched on and off in FIG. 1; and

FIG. 4 is a graphical representation of the flux density andmagnetization as a function of time of the magnetic valve in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, andin particular to FIG. 1, the magnetic valve 10 includes a pretensionedspring 11 which operates in the closing direction, upon an armature 12which is movable subjected to a magnetic field. The closure of themagnetic valve results from the aid of a closing member or closuremember 13 which is operatively connected to the armature 12. The closuremember 13 has a conically shaped portion which is fitted into a valveseat 14. The fuel to be sprayed by the magnetic valve is applied throughthe entrance 15. The operating coil 16 of the magnetic valve has acenter tap 17, as well as the two terminals 18 and 19. The center tap 17is connected directly to the positive terminal of a voltage operatingsource U,,. The terminals 18 and 19 are each connected to collectors oftransistors of the npn type in the form of power transistors T10 andT11. Thus, the terminal 18 is connected to the collector of T10, whereasterminal 19 is connected to the collector of T11. The emitter of thepower transistor T10 is connected to the emitter of the power transistorT11, and both emitters are joined to the voltage supply line 25connected to ground potential.

The base of each power transistor T10 and T11 leads to the voltagesupply line 25, through a circuit consisting of a resistor connected inparallel with a capacitor. Thus, for the power transistor T10, theresistor R10 is provided in parallel combination to the capacitor C10.Similarly, associated with the transistor T11, is the parallel circuitof resistor R11 and capacitor C11. The collector of a control transistorT12 is connected to a circuit junction 26, whereas the emitter of thiscontrol transistor T12 is also connected to ground potential through thevoltage supply line 25. Connected, furthermore, to the circuit junction26, is the base of transistor T10, through the series circuit consistingof resistor R12 and diode D10. The base of transistor T11 is similarlyconnected to the circuit junction 26, through the series circuit ofresistor R13 and diode D11. The cathode of the two diodes D10 and D11are directly connected to the bases of the two transistors. The powertransistor T10 operates in conjunction with the diode D10 and resistorR12, whereas the power transistor T11 operates in conjunction with thediode D1 1 and resistor R13. Connected, furthermore, to the collector ofthe transistor T11, is the series circuit consisting of capacitor C12and resistor R14. This series circuit of the latter components is,moreover, connected to the anode of the diode D10, the cathode of whichis connected to the base of the power transistor T10. Similarly, thecollector of the power transistor T10 is coupled to the anode of thediode D11, through the series circuit consisting of capacitor C13 andresistor R15. The cathode of the diode D11 is directly connected to thebase of the power transistor T11. The collector of the controltransistor T12 which is joined to the circuit junction 26, leads to thepower supply voltage U,, through a resistor R16. The emitter of thecontrol transistor T12 is directly connected to the ground voltage line25.

FIG. 2 shows two diagrams with two magnetizing characteristics whichapply to the magnetic valve 10, and in particular to the ferromagneticparts thereof. The left diagram in FIG. 2, provides the generalmagnetizing characteristics for a magnetic valve which is notdemagnetized. In the state in which current flows, a maximum fieldstrength Hm prevails, and a corresponding flux density Bs prevailscorrespondingly to the field intensity I-Im at the armature, forexample. The flux density Bs appears at the beginning of saturation ofthe iron.

When the current is now turned off, the field intensity H becomes zero,so that the magnetic flux density B takes the path of the upper curve inthe direction from ES to Br. The flux density Br is the residual fluxremaining when the field intensity H is zero. The iron parts of thearrangement used in the operation of the magnetic valve, therefore,always possess magnetic properties in the un-excited state of theassociated electromagnetic coil. This remaining magnetic property in theform of residual magnetic flux, causes an attractive force between thearmature and the remaining ferromagnetic parts of the valve. In orderthat the magnetic valve remains securely closed in the unexcited stateof the coil, however, the force resulting from the residual magnetismmust be supplemented through the oppositely directed force applied bythe spring 1 1.

The diagram at the right hand of FIG. 2, shown as FIG. 20 on thedrawing, shows the function of the flux density or magnetization B as afunction of the field intensity H when the ferromagnetic parts of themagnetic valve are de-magnetized. The flux density B then becomes zerowhen the voltage applied to the electromagnetic coil is removed orturned ofl". As a result, the closure force which is required to retainthe magnetic valve in the closed state, can then be made considerablysmaller. If a de-magnetized valve is connected to the operating voltagesource again, considerably larger forces may be used for acceleratingthe armature, when the construction of the magnetic valve remains thesame. This is because the magnetic forces opposite to the force appliedby the spring 11, may be reduced as a result of the decrease or completedropout of the residual magnetism. When taken in conjunction with thediagrammatic characteristics in FIG. 2, the operational function of FIG.1 may be readily described. This operation of the arrangement of FIG. 1is as follows:

The resistor R16 which is connected between the junction point 26 andthe operating voltage U serves as the collector resistance for thecontrol transistor T12. When the control transistor T12 becomes turnedoff through the control voltage U applied to its base, a potential isapplied to the bases of the power transistors T and T1 1 through theresistor R16. This voltage applied to these bases is transmitted throughthe feedback branches R14, C12, and R15, C13. With these feedbackbranches, the circuitry functions as a multivibrator. The diodes D10 andD11 protect the base-emitter paths of the power transistors T10 and T11,from being subjected to voltages of excessive magnitudes. Since theconstruction and operation of multivibrator circuits are well known inthe art, the details of this circuit are not further described here. Thetransistors T10 and T11 are alternatingly in the conducting and cut-offstate. As a result, current flows alternatingly through each halfwinding of the tapped coil of the magnetic valve. With each switching ofthe multivibrator, the flux density changes in the magnetic circuit ofthe valve. The change of the flux density, in this manner, is withrespect to its sign or polarity. If, now, such a control voltage isapplied to the control transistor T12, so that the latter becomesconducting, a voltage drop appears across the resistor R16 to the extentthat the power transistors T10 and T1 1 become turned off through thevoltage divider consisting of resistors R12, R10 and R13, R11. Themultivibrator commences thereby to cease operation by ceasing tooscillate. The oscillations of the multivibrator are thereby relatedwith the rise of the control voltage U so that the ferromagnetic partsof the magnetic valve 10 become thereby de-magnetized.

These processes are illustrated graphically in FIGS. 3 and 4. FIG. 3shows the voltage U as a function of time, whereas FIG. 4 shows theresulting magnetic flux density B as a function of time, whenprevailing, for example, at the armature of the magnetic valve 10. Thefunction of the flux density or magnetization of FIG. 4 is representedin ideal form. The selfinduction of the operating coil which has theeffect of providing rounded comers on the curve, has been neglected.These simplified curves, however, are very close to the actual function,since the inductance of the operating coils is to be maintainedsubstantially small.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied inmagnetic valve operating circuits, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. An arrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valve, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangular-shaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; voltage dividing means connected to each base of saidpower transistors for providing a supply voltage thereto; and a sourceof operating voltage connected to said voltage dividing means.

2. An arrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valve, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangular-shaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; voltage dividing means connected to each base of saidpower transistors for providing base supply voltage thereto; a source ofoperating voltage connected to said voltage dividing means, said voltagedividing means comprising a first resistor connected to said source ofoperating voltage, a second resistor connected between said firstresistor and the base of one of said power transistors, and a thirdresistor connected between said first resistor and the base of the otherone of said power transistors, said first transistor having one terminalconnected to a terminal of each of said second and third resistors.

3. An arrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valve, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangular-shaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; and a source of DC. operating voltage, said coil foroperating said valve being a center tapped coil with center tapconnected to said source of DC. operating voltage, each end terminal ofsaid center tapped coil being connected to one collector of said powertransistors.

1. An arrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valVe, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangularshaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; voltage dividing means connected to each base of saidpower transistors for providing a supply voltage thereto; and a sourceof operating voltage connected to said voltage dividing means.
 2. Anarrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valve, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangular-shaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; voltage dividing means connected to each base of saidpower transistors for providing base supply voltage thereto; a source ofoperating voltage connected to said voltage dividing means, said voltagedividing means comprising a first resistor connected to said source ofoperating voltage, a second resistor connected between said firstresistor and the base of one of said power transistors, and a thirdresistor connected between said first resistor and the base of the otherone of said power transistors, said first transistor having one terminalconnected to a terminal of each of said second and third resistors. 3.An arrangement for reducing the response time of a magnetic valvecomprising, in combination, an electromagnetic coil in said magneticvalve for operating said valve upon applying an actuating signal to saidcoil; a source of alternating voltage providing an alternating voltageof predetermined frequency; connecting means between said source ofalternating voltage and said electromagnetic coil for applying saidvoltage to said coil before or after operation of said valve, so thatsaid valve is de-magnetized through application of said alternatingvoltage to said coil, whereby residual magnetism in said electromagneticcoil is substantially removed through said demagnetization of said valveprior to a subsequent operation of said valve, said residual magnetismincreasing the response time of said valve to said actuating signal,said source of alternating voltage comprising an oscillator; controllingmeans connected to said oscillator for turning said oscillator on andoff, the output voltage of said oscillator being substantiallyrectangular-shaped, said oscillator comprising an astable multivibrator,said astable multivibrator comprising two power transistors and acontrol transistor connected across the base supply voltage for saidpower transistors; and a source of D.C. operating voltage, said coil foroperating said valve being a center tapped coil with center tapconnected to said source of D.C. oPerating voltage, each end terminal ofsaid center tapped coil being connected to one collector of said powertransistors.